1. Field Of The Invention
This invention relates to coupling means for tubular elements and, ore particularly, to a readily detachable coupling capable of taking axial and torsional loads.
2. Background Of The Invention
The prior art shows a great variety of couplings for making a readily attached and detached connection between tubular elements. Because of their convenience, various types of snap ring or ring-type key connections have become popular for such couplings. Usually such constructions employ opposed annular grooves in overlapping portions of the elements being joined and the ring or key adapted, when the coupling is assembled, to extend into the grooves and thereby lock one element in position with the other. Although such an arrangement usually makes a satisfactory coupling when axial loads on the coupling are involved, they leave much to be desired when the coupling is subjected to torque loads.
When the coupling is required to withstand torque as well as axial loads, a threaded connection is generally employed. To reduce the number of turns required to engage a large number of threads and also to provide a seal for pressurized fluids when a threaded connection is used with tubes or pipes conveying fluids, pipe threads are used instead of machine threads. In some threaded connection designs, a shoulder is incorporated on one of the elements of the connection to act as a jam nut. When the other element of the connection is tightened against the shoulder, the "play" is taken out of the joint and the bending rigidity of the coupling is increased. Threaded connections have a number of drawbacks that tend to limit their usefulness. The principal disadvantages of conventional threaded connections include the following: the loads on the joints are statically indeterminate and minute dimensional variations in the threads can produce large variations in the load distribution on the threads; threads are inherently structurally weak in comparison with the tubes or pipes in which they are formed and are hence subject to high stresses and stress concentrations; threads are easily damaged by rough handling; and for critical applications, the inspecting of new or renewed threads is difficult and expensive. In addition, threaded joints are unidirectional and a torque in the wrong direction tends to unscrew the connection. On the other hand, excessive torque loads in the thread direction has a tendency to jam the connection. In addition, threaded connections normally require the use of tools to make and break the coupling.